Sulphur dioxide, ozone, PM10... any of these run through your mind as you style your hair each morning? If you're a city dweller, your hair is immersed in millions of these toxic molecules every day. And they have all the ammunition necessary to utterly ravageyour hair.

Pollution in our hair. . .

Overall air pollution in the UK has certainly been on the wane since the infamous Great Smog of London in 1952. Back then, the thick fog blanketed the city for five days, reducing visibility to barely a metre and even creeping inside buildings. Thousands lost their lives as a result, either from accidents due to poor visibility, or illnesses caused by the pollutants. This tragedy drew the impact of pollution sharply into the nation's focus, triggering radical political and industrial change, including the landmark Clean Air Act of 1956. Yet, over 60 years later, we still get bombarded with harmful, airborne chemicals every time we step out of our homes – and sometimes inside them, too. While the coal fires that fuelled the Great Smog have largely been replaced by cleaner power sources, levels of pollution are still a cause for concern. What comes as a surprise, is that they can have aesthetic as well as environmental consequences.

What are these pollutants and how exactly do they affect our hair?

The main culprits are mostly airborne pollutants, including volatile organic compounds like benzene, a component of petrol, plus sulphur dioxide, nitrogen dioxide and ozone.

There's also particulate matter (aka PM1, PM2.5 and PM10), which is ultrafine dust composed of a mix of of soot, burnt wood, plus power plant and vehicle emissions.

And last, but by no means least, tobacco smoke.

Together, these pollutants do to your hair pretty much all the things you use shampoo, conditioner and good haircare period, to prevent. For example, they...

Take your shine away Volatile organic compounds, particularly from petrol, adsorb to your hair, leaving a layer of grime. Particulate matter also powders your hair in its dust, leaving it dull, listless and rough to the touch.

Make your hair extremely dirty, extremely quickly

In random hair pollution tests carried out in Milan – a city notorious for its traffic – hair and scalps scanned with high-powered microscopes revealed not only pollution-coated strands, but also shadowy grime on the scalp of testees.

Break your hair, literallyMany of the airborne pollutants that stick onto the surface of our hair are also light sensitizers; they make your hair more vulnerable to molecules that attack it in the presence of sunlight.

Molecules like the hydrocarbons that are released into the air when petrol is burned, and other pollutants such as nitrogen dioxide and sulphur dioxide. Once the sun's rays hit them, these substances happily undergo photochemical reactions, creating secondary pollutants. The most notorious of these is ozone, a free radical that viciously attacks your hair, skin, trees, buildings, metal structures... nigh on everything in sight.

When it comes to your mane, ozone does its damage by oxidising the hair, breaking its disulphide bonds just like a relaxer. Since disulphide bonds are responsible for your hair's overall stability and structure, when they are lost, your hair loses elasticity and snaps easily.

In turn, the hair shaft also becomes more porous; part of a vicious cycle which makes it easier for these compounds to stick to its surface, causing even more of the same destruction. Once pollutants leave your hair light-sensitized, the damage that results is ashocking 20-40%.

Become a part of your new growth

While several pollutants can easily float their way onto the surface of our hair, some can also get into our hair in a much more sinister and insidious way.

As airborne pollutants are mostly gases and fine particles, we breathe them in all the time. Anything we ingest goes directly into our bloodstream – the exact place from which our hair collects the parts it uses to grow.

Growing hairs actually bind these pollutants onto the melanin of the shaft, building them into your hair. So the pollutants you inhale today will, in a month's time, be about a centimetre away from your hair's root.

Leave you grey When pollution affects hair deep down in the scalp, it can cause inflammation of the dermal papilla. This inflammation can in turn cause the hair to lose the ability to pigment itself. The results? Premature grey strands, even on teens and twentysomethings.

Make your hair fall out Pollution has been linked to baldness. A study carried out by the University of London, confirmed airborne toxins' role in hair loss. Researchers think that any toxin which can make it into the bloodstream, and into the hair follicle, can stress it out, eventually affecting its ability to produce a fibre.

Tobacco smoke came in for particular scrutiny; scientists found that fumes from cigarettes reduced scalp circulation, causing the capillaries to constrict, which cuts the flow of nutrients to the roots. This reduction in the supply of the materials used to construct and repair the hair sparks a whole host of troubles for nicotine-damaged hair cells, from follicle damage, to throwing hormones off balance – eventually triggering shedding.

And remember that same tobacco-induced inflammation which leads to greyness? It also accelerates hair loss. On top of all this, tobacco fumes have long been linked to DNA damage, and damaged DNA is another factor associated with androgenic alopecia (hereditary hair loss).

The worst bit While the ill effects of pollution on our tresses are certainly perturbing, what's especially chilling is the way these contaminants affect our bodies and the ecosystem we depend upon to live. Its effects on plants and animals threaten species and even the food supply. Nitrogen dioxide, sulphur dioxide and ozone all irritate our airways, and, due to their tiny size, particulate matter can be breathed deep into the lungs, where they can cause inflammation and worsen lung disease. As well as respiratory conditions like asthma and bronchitis, common everyday pollutants are linked to cancer, heart attacks and strokes. The numbers certainly put things into perspective: in 2011, over 50,000 deaths in the UK alone were due to the effects of pollution.